In previous electrophysiological experiments performed by the Principal Investigator on the Pacinian corpuscle, a mammalian mechanoreceptor, graded receptor potentials were measured in response to sinusoidal-displacement stimuli. Those results suggested that there are two populations of transducing elements with each corpuscle, each group having its own directional specificity. Using neurophysiological and anatomical techniques, we plan to link the response properties of these elements to their physical structure. Evidence indicates that these elements are the cytoplasmic extensions of filopodia which emanate from the receptor's axon these elements resembling neuronal growth cones. The filopodia presumably contain actin microfilaments and have been described in many other mechanoreceptors, implying perhaps a similar mechanism for mechanotransduction across receptor types. Using neurophysiological and anatomical (light and electron microscopy) techniques, we plan to test the hypothesis by performing several experiments, specifically designed for that purpose. These include: a) assessing the effects of stimulus probe dimensions into and around the corpuscle; b) measuring the effects of stimulus attack angle by rotating the stimulus probe around the receptor's surface, and c) using tritiated and/or fluorescent neurotoxins specific to the transduction process to help identify the sites of transduction. The significance of the research, in addition to describing possible general mechanisms for transduction, lies in the fact that the Pacinian corpuscle is ubiquitous in the human integument and has been shown to mediate a substantial proportion of the human somatosensory experience. Determining the manner in which Pacinian corpuscles transduce mechanical deformations into neural signals may add significantly to the understanding of the mechanisms involved in the experience of touch.
